Sliding door hanger



Aug- 11, 1964 F. s. DUNHAM 3,143,758

SLIDING nooR HANGER Filed Feb. 9, 1960 FREDERICK SMA/L57 l/NHM INVENTOR United States Patent Oilce 3,143,758 Patented Aug. 1l, 1964 3,143,758 SLlDING DOOR HANGER Frederick Stanley Dunham, East Orange, NJ., assigner to Otis Elevator Company, New York, N Y., a corporation of New Jersey Filed Feb. 9, 1960, Ser. No. 7,593 1 Claim. (Cl. 16-88) This invention relates to linear type door hangers, and particularly to such hangers arranged for supporting doors for sidewise movement to control access to the entranceways of railway cars, elevator cars and like apparatus.

Generally speaking, such cars are used in locations that are subject to considerable dust of various types. This is particularly true f railways cars used in metropolitan subway systems where they operate within contining tunnels.

One popular linear type of hanger used in subway cars employs an inner track and an outer track which are joined together by two sets of anti-friction means, such as ball bearings, which operate in runs in the contiguous surfaces of the tracks. The outer track, which has roughly an inverted U-shaped cross-section is aiixed to the structure above the entranceway. The inner or center track, which is movably supported within the outer track by the bearing means, is affixed to the top edge of the door and is movable within the outer track to permit the door to be moved sideWise to open and close the entranceway.

Since in such a hanger the ball bearings support the full weight of the door and center track, the ball bearings have in the past been made of metal which are undesirably noisy in operation. In order to minimize such noisy operation and also to reduce further the frictional engagement between relatively moving parts, it has been the practice periodically to lubricate the bearings in their runs in their tracks. This lubrication has in turn acted to collect or trap an undesirable amount of the surrounding dust, some of which is from the metal brake shoes which engage the wheels of the car. As the entrapped dust, adhering to the lubricant, accumulates, a thick abrasive compound is formed which acts to impede operation and to damage the tracks and the movable bearings, eventually resulting in noisy door operation.

To prevent the accumulation of this abrasive dust and to impede its abrasive action, it is customary routinely to remove the cars from service for inspection and for removal of the abrasive material. In addition to decreasing the number of cars that are available for service at any given time this routine inspection and maintenance involves considerable labor efforts, since it is necessary t0 remove the door and dismantle the hanger to gain access to gain access to the moving parts.

It is therefore an object of this invention to provide a linear type hanger for a sliding door which is quiet in operation and which is of such character that little or no periodic maintenance is required to maintain its cleanliness.

It is also an object of this invention to provide in such a hanger anti-friction means in the form of ball bearings, which are of such character that no lubrication is required, but which are of themselves durable enough to withstand the customary service requirements of substantially the life of the car.

In carrying out the invention, the hanger is provided with ball bearings made of a material which is self-lubricating, yet non-soiling as it has for all practical purposes no anity to dust and like particles and which is resilient enough to be quiet in operation and yet can support moderate loads.

Features and advantages of the invention will be seen from the above and from the following description when considered in conjunction with the drawings and appended claim.

In the drawings:

FIGURE l is a front elevational View of a hanger that is supporting a sliding door (only the top portion of the door being shown) in its closed position and with the open position indicated by dot-dash lines;

FIGURE 2 is an enlarged cross-sectional view taken along line 2-2 of FIGURE l; and

FIGURE 3 is an enlarged fragmentary view of the right end of FIGURE l taken along line 3 3 of FIGURE 2.

Referring to the drawings, sliding door 10 is suspended from an overhead horizontally disposed hanger, generally designated 12. Overhead hanger 12 is in turn suspended at its ends and midsection from L-shaped mounting brackets 14 bolted to the structure 15, forming the entranceway. The hanger is approximately twice the width of door 10 and extends from one side to approximately the doors width beyond the other side of the entranceway. Essentially, hanger 12 comprises a stationary tube track 17 approximately twice the Width of the door; a movable center track 18 within tube track 17 and held in rolling suspension therein by means of ball bearings 20, and a ball retainer 22 adapted to t within tube track 17 and maintain ball bearings 2t! in spaced relationship with each other. Center track 18 to which sliding door 10 is attached extends longitudinally, preferably, slightly less than the door width, while retainer 22 extends longitudinally approximately one and a half times the width of door 1t).

Tube track 17 is of substantially inverted U crosssectional shape having a horizontally disposed web portion 26 connecting two downwardly extending flange portions 24, 25 each of which is expanded outwardly to form on the inside surfaces two horizontally parallel and oppositely disposed ball races 27, 29 that extend the full length of the track. Tube track 17 is reinforced at suspension points by channel members 33, the depending flanges 35, 36 of which engage the outer surfaces of flanges 24, 25, respectively, of the tube track. At each suspension point a suspension bolt 32 passes through aligned apertures formed in web 26 of tube track 17, web 37 of reinforcing channel member 33 and the horizontally extending iiange portion 41 of mounting bracket 14, and in co-operation with nut 38 and lock washer 39, secures the tube track to the mounting bracket.

Center track 18 has a substantially rectangular crosssectional shape with the widest sides of the rectangle disposed vertically. Horizontal ball races 43, 44, are formed in the upper portion of each vertical side and extend along its entire length. These races are of the same size as races 27, 29 formed on the inside surfaces of anges 24, 25 of tube track 17 and co-operate with them t0 form ball raceways on either side of center track 18.

The lower portion of center track 13 is positioned in reinforcing channel 46 which forms the top edge of door 10. Barrel bolts 52, passing through apertures formed in the door and center track 18, attach the door to the center track.

Ball elements 20 fit co-operating races 27, 43 and 29, 44 and are positioned therein on either side of center track 13 to hold the center track rmly in rolling suspension within tube track 17. The balls 20 are formed of a self-lubricating plastic compound, such as polytetraliuoroethylene, commercially known as Teflon whose monomer formula is C2F4, and which hereinafter is referred to as Teflon. Teflon is non-soiling and resilient. The Teflon balls are maintained in linear and spaced relationship from each other in their raceways by means of retainer 22, which retainer allows each ball to turn freely in place.

Retainer 22 is a channel member substantially nverted U cross-sectional shape, having downwardly extending parallel flange portions 55, 56. Flanges 55, 56, respectively, have spaced ball receiving apertures formed therein. Two lip portions 58, projecting inwardly, are formed in each aperture in position and curved to fit the front and back'of each Teon ball 20. These lipy portions hold each ball from falling through its respective aperture when the ball is inserted into the retainer. When the hanger is assembled and center track 18 is inserted between the parallel downwardly extending flanges 55, 56 of retainer 22, center track ball races 43, 44 engage balls 20 and press them clear of the retainer into engagement with ball races 27, 29 of tube track 17. As center track 18 is moved sidewise, each ball contacts retainer 22 only at the lip portion 58 in the direction of travel of the center track. Thus, Teon balls 2i) are retained in spaced relationship with each other but are free to turn in retainer 22 in the direction of travel by pressing against the curved lips 58 rather than the sharp edges of the aperture which might soon deform the balls. Retainer 22 is prevented from rolling out of the ends of tube track 17 by a downwardly extending projection 6) formed on the outside end of each of the reinforcing channel members 33 which are positioned at the ends of tube track 17, the projections 60 acting as stops.

It is to be understood from the foregoing that with the hanger parts assembled as described, the tubetrack and center track are Vin rolling engagement with the Teflon balls in the retainer, which retainer is also free to move with respect to both tracks. As the door moves sidewise, the center track from which it is suspended moves twice the distance at twice the speed that the retainer moves but with only the rolling friction of the balls in the raceways to overcome.

As has been previously stated, overhead hangers using metal balls are noisy and therefore require periodic lubrication. When lubricated, dust andtdirt collect in the lubricant, necessitating periodic dismantling and cleaning of the hanger to insure proper operation thereof. Unlike such hangers, the subject hanger, due to the selflubricating, non-soiling characteristics of the Teon balls, requires no lubrication and therefore remains relatively free of dirt, and yet, due to the resiliency of Teflon, is quiet in operation. This obviates the necessity for periodic lubrication and cleaning of the hanger and the resulting loss of service of the equipment upon which it is arranged.

This is an unexpected result, since it has been generally known that, though Teflon is a thermoplastic with a very low coecient of friction (static against polished steel .09-.12, inclined plane test method), is self-lubricating and non-soiling and therefore desirable as a bearing material, it is easily dented, scratched, is relatively soft and is ordinarily susceptible to cold flow (creep). These latter characteristics of Teflon, it was thought, made it unacceptable, unless mechanically reinforced, for use as a bearing material. This is especially true for stressed applications, such as the subject hanger wherein the Teflon ball bearings support the weight of the door and center track (approximately 80 pounds) and the operating forces applied to open and close the door may also stress the ball bearings. For example, see the patent to Tait, #2,691,814 wherein at column 1, lines 34-35, Tait recognizes the low mechanical strength of Teon and therefore limits the use of Teflon to plane bearings for sliding contact applications only, such as bearing sleeves, bearing liners, thnlst washers, etc. (see Tait, column 1,

lines 1-4), which applications are relatively low stressed ones compared with ball bearings to which point contact loads are applied. Even so, Tait does not form his plane bearings from Tefion alone but, rather, impregnates a spongy metal with Teflon and places this impregnated metal on a rigid metal backing in order to obtain a plane bearing of 'suticient mechanical strength. In other words, Tait, rather than use Teflon as a bearing material, merely uses it as a lubricant by impregnating the spongy material to form a relatively low friction surface for use as a bearing surface.

The subject hanger has been installed on subway cars and tested for substantial periods under service conditions.

Under such conditions it has been found to operate quietly and has remained free of abrasive dust. In actual use the hanger requires no cleaning and is much quieter in operation than hangers equipped with ball bearings made of metal. Accelerated life tests were also performed which indicated that the subject hanger, using Teflon balls, showed no deterioration in utility or efciency for the expected life of a subway car (25 years).

As changes can be made in the above described construction and many apparently different embodiments of this invention can be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown on the accompanying drawings be interpreted as illustrative only and not in a limiting sense.

What is claimed is:

A linear type ball supported sliding door hanger for movably suspending a vertically disposed horizontally sliding door, said hanger comprising a pair of straight track members one of which is centrally located and movable longitudinally with respect to the other and when so located is adapted for suspending said sliding door forming a load, the other track member being stationary and having substantially an inverted U cross sectional shape with its downwardly depending legs substantially parallel to the opposed vertically disposed sides of said between said track surfaces Vfor the suspensionY of said door, a ball retaining member having ball carrying portions extending into said raceways between said tracks and being adapted to maintain adjacent ones of said ball elements separated from each other, each and all of said load supporting ball elements being composed of polytetrailuoroethylene.

References Cited in the file of this patent f UNITED STATES PATENTS 1,259,261 Mears Mar. 12, 1918 2,400,099 Brubaker et al. May 14, 1946 2,609,256 Baker et al. Sept. 2, 1952 2,835,540 Jorgensen May 20, 1958 2,846,251 Herbenar Aug. 5, 1958 2,848,734 Ault Aug. 26, 1958 2,975,128 Stott Mar 14, 1961 

